1. Field of the Invention
This invention relates to a hand-held device for transferring a film from a carrier tape to a substrate.
2. Discussion of the Related Art
One such device is described in DE 38 32 163 A1. In this case, the applicator consists of an application foot which is provided at its free end with a thin-lipped application toe to guarantee flutter-free application of the film transversely of the longitudinal axis of the carrier tape, as required for example in the transfer of a cover-up film from the carrier tape to the substrate. The films used are mainly adhesive films or cover-up films.
The thin-lipped application toe contains the contact surface and provides for uniform pressing of the film-coated carrier tape against the substrate surface, even where the substrate is elastic and/or uneven, such as a work surface. This construction is designed in particular for application of the film to the work surface in the pull mode of operation.
Hand-held devices designed both for pulling and for pushing application of the film to the work surface are a more recent innovation. The push mode of such devices affords the advantage that, for example for delicate cover-up tasks, such as text corrections, the beginning and end of the text to be corrected are easy to see and are not covered by the device, as is the case with transfer in the pull mode.
One such hand-held device, comprises a housing from which projects a supporting foot with an applicator roller at its free end as the applicator. To transfer the film to the substrate, the film-coated carrier tape coming from a supply roll is guided to the applicator roller where it can be pressed against the substrate by a first contact surface or a second contact surface depending on how the device is held, i.e. depending on whether the device is to be operated in the pull or push mode. After the film or film layer has been transferred to the substrate, the empty tape is guided to the take-up spool.
If the two operating modes, i.e. the pull mode and the push mode, are to be employed as and when required, the applicator must be substantially symmetrical in construction because, to change the mode of operation, the hand-held device has to be turned through 180.degree. to apply the other contact surface to the work surface formed by the substrate. Since the carrier tape, when it is being offwound from the supply roll, has to drive the supply roll, including its core and rotatable mounting, and also a slipping clutch and the take-up spool for taking up the empty tape, including its core and rotatable mounting, torques are generated which have to be overcome by the adhesion of the film to the substrate because otherwise the film will tear and/or the transport of the carrier tape will stop.
Although an applicator roll is suitable for the pull and push modes of the hand-held device, it does not guarantee flutter-free application of the film at a right-angle to the longitudinal axis of the carrier tape, as required for the transfer of a cover-up film to a substrate and as can be achieved by using an application toe as the applicator.
Tests with application toes have shown that, depending on the adhesiveness of a film, its use presupposes a minimum contact surface between the film and substrate which is determined by the width of the carrier tape and the contact length of the carrier tape on the substrate. In addition, a user must not be confined to one particular angle of application of the hand-held device in operation, instead the device should also operate reliably at angles of application selected individually within certain limits which can be achieved by making the contact area, i.e. the particular contact surface, preferably round in shape.
Accordingly, known hand-held devices for transferring a film from its carrier tape to the substrate by push or pull application have a radius of curvature of the application toe of 0.4 to 0.6 mm which leads unavoidably to a thickness of the application toes that rules out elastic adaptation to the substrate. However, since there is a lower limit to the radius of curvature, the advantages of the application toe used in the hand-held device according to DE 38 32 163 A1, including for example elastic adaptation to an uneven substrate and exact application of the film layer, cannot all be achieved in a hand-held device designed for both push and pull operation either with a known application toe or with an applicator roll.